30(!) years ago as a young student I made 6 speaker sets based on the KEF CS3 design, together with a subwoofer.
I even found the drawings on this site.KEF CS3

It was really ‘value for money’ because I am still a happy user after all these years, using them on a daily basis!
The amplifiers etc changed, but never my speakers.
Probably you ‘experts’ would call me insane that I still use them, but I still love them.

However, finally one of the speakers, a KEF B200.G. SP1075 broke down (shame of course )

I am not an expert on these things, so could you please advise me which currently available speaker I could use for a replacement for this one?
(Probably replace the others as well)

I would have the loudspeaker repaired, there are a few good places in the UK which can do this. Being as the DIY community in mainland Europe appears more active than the UK I'd check for any such similar offerings nearer to you._________________I contend that for a nation to try to tax itself into prosperity is like a
man standing in a bucket and trying to lift himself up by the handle.
-Winston Churchill